Heat exchanger

ABSTRACT

The heat exchanger is self-supporting in that one tube system of co-axial tube cylinders is supported within a second tube system formed of a skeleton of tubes. Both systems are connected to common distributors and headers and both are enclosed by a cylindrical casing of helically coiled tubes. A muffle burner is located coaxially of the first tube system to direct a flow of heat exchange medium into the heat exchanger.

United States Patent IIQI IIII 3,757,746

Sharan [45] Sept. 11, 1973 [54] HEAT EXCHANGER 2,597,423 5/1952 woynar 122/250 R [751 invento arend/:a zal s hafa, FOREIGN PATENTS R APPLICATIONS seuzac /Z Swtzerand 1,028,525 /1966 Great Britain I 165/145 [73] Assignee: Sulzer Brothers Ltd., Winterthur, 1,060.382 7/1959 Germany 165/163 Switzerland I,0s3,526 6/1960 Germany... I22/25o R 1,025,437 3/l958 Germany 165/163 [22] Filed: May 3, 1971 [2l] Appl. No.: 139,601 Primary Examiner--Albert W. Davis, Jr.

Attorney-Kenyon & Kenyon Reilly Carr & Chapin Foreign Application Priority Data May 8, i970 Switzerland 6861/ [57] ABSTRACT [52] Us. CL i l n l n 122/250 R 165/145 165/163 The heat exchanger is self-supporting in that one tube v /172 system of c0-axial tube cylinders is supported within a [5 I] Im. CI. Fzzb 21/26 Second tube System formed 0f a Skeleton Ofubee Both [58] Field of Search 165/163 162 145 Systems are Connected to common distributors and A 165/157 A 172. n2/i5() R' headers and both are enclosed by a cylindrical casing of helically coiled tubes. A mule burner is located co- [56] References Cited axially of the first tube system to direct a flow of heat UNITED STATES PATENTS exchange medium into the heat exchanger.

3,446,188 5/1969 Nozawa et al. 122/32 13 Claims, 2 Drawing Figures PATENYEDSEPT |973 3. 757, T116 snm 2 nf 2 Fig. 2

HEAT EXCHANGER This invention relates to a heat exchanger and more particularly to a heat exchanger for generating hot water or steam.

I-leretofore, heat exchangers, especially those for generating hot water or steam, have been constructed with a tube system for carrying a heat exchange medium and a support structure for supporting the tubes of the tube system relative to one another. However, these support structures have generally been uncooled during operation of the exchangers. As a result, the highest temperature of the heat exchanger medium has been limited since the support structures may be deleteriously effected should excessively high temperatures occur within the heat exchanger. 1n addition, these support structures have frequently required suitable means for damping any vibrations of the tubes within the heat exchangers. Thus, the cost of these heat exchangers has been increased.

Accordingly, it is an object of the invention to provide a heat exchanger of simple construction which is capable of using heat exchange media of relatively high temperature. .t

lt is another object of the invention to eliminate the use of uncooled support structures in a heat exchanger.

It is another object of the invention to obtain an efficient heat exchanger of low cost construction.

It is another object of the invention to obtain a heat exchanger of compact construction.

Briefly, the invention provides a heat exchanger with two tube systems for a heat-exchanger medium. The first tube system includes a plurality of co-axial tube cylinders wherein each cylinder consists of at least one helically coiled tube while the second system includes a skeleton of tubes between the cylinders of the first system. The second tube system is also connected to a distributor situated at one end of the tube cylinders of the first tube system.

This heat exchanger has the advantagev that the second tube system forming the skeleton does away with the need for any uncooled means for mounting the tube cylinders of the first tube system relative to one another. Consequently, the effective heat exchanger surface that can be accommodated in a given volume is increased while, on the other hand, a heat exchanger medium at very high temperature, eg., 2,000C, can be used to heat the heat exchanger. Thus, the overall result is a very compact heat exchanger construction which provides trouble-free operation since the skeleton prevents or reduces any vibration of the coils of the tubes of the tube cylinders. The production of the heat exchanger is simple and cheap because the tube cylinders may be manufactured in a continuous bonding process.

The heat exchanger also includes a muffle burner for the production of a heated gas or second heat exchanger medium. The muffle burner is located within the heat exchanger so that the axis of the mufe of the burner is parallel to the axis of the tube cylinders. The use of a muffle burner in which combustion is completed in the muffle thereby allowing the tube systems to be heated by convection so that no flames emerge from the muffle, has the advantage that the tubes of the heat exchanger are subjected to uniform thermal loading.

Conveniently the tube cylinders are surrounded by a cylindrical casing of tubes which are welded together in sealing-tight relationship. The advantage of this is that the space through which the first heat exchange medium flows is uniformly and densely filled by heat exchange tubes. Also, this construction is favorable if internal pressure occurs either as a result of the use of booster systems or an explosion. Further, no special supporting means, e.g., flanged girders, are necessary for the heat exchanger casing.

These and other objects and advantages of the invention will become more apparent from the following detailed descriptionand appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates an axial sectional view through a heat exchanger according to the invention; and

FIG. 2 illustrates a plan view of the heat exchanger of FIG. l, the muffle burner having been omitted.

Referring to FIG. 1, the heat exchanger incorporates a first tube system consisting of six coaxial tube cylinders, 4, 5, 6, 7, 8, and 9. In addition, a second tube sys tem is provided which forms a skeleton and serves to space apart the tube cylinders 4 to 9. This second tube system consists of four groups of tubes, each of which is situated in a radial plane (cf. FIG. 2), viz. 11, 12, 13, 14 and 15; 16, 17, 18,19 and 20; 2l, 22, 23, 24 and 25; and 26, 27, 28, 29, and 30. Of these four tube groups, only the groups of tubes 1l to 15 and 16 to 20, together with the tubes 21 and 22 are shown in FIG. 1. The tubes of these four groups extend axially between the six tube cylinders 4 to 9 and pass from four distributors 31, 32, 33 and l34 for the heat-absorbing medium, e.g., water, and lead at the top into four headers 36, 37, 38 and 39. (FIG. 2 shows the connection of the skeleton tubes 23-25 and 26-30 not visible in FIG. 1 to the headers 38 and 39.) The innermost tube cylinder 4 is formed from three contiguous helically coiled tubes l, 2 and 3 while the tube cylinder 5 consists of two helically coiled tubes 51 and 52 between the coils of which some space is provided. The tube cylinders 6 and 7, in turn, consist of three helically coiled tubes 60, 61 and 62; 70, 71 and 72, while the tube cylinders 8 and 9 are formed from four and five tubes respectively, 80, 8l, 82 and 83; and 90, 91, 92, 93 and 94. In FIG. 1, the cross-section of one and the same tube in each tube cylinder is marked by a cross.

Apart from the tubes 11 to 30 forming the skeleton, the tubes of the tube cylinders 4 to 9 are also connected to the distributors 31 to 34 and the headers 36 to 39, so that all the tubes are connected in parallel with respect to the flow of heat-absorbing medium. In FIG. 2, the individual tube cylinders are shown as chain-dotted circles and in each case that end of the tubes forming the tube cylinders which emerges from the drawing plane has been illustrated. The four headers 36 to 39 with the tube connections are also shown, and the association between the tubes and the headers will be apparent from the numbering of the tube ends and the tube connections. The tubes are connected correspondingly to the distributors 3l to 34.

Additional tubes 15'20', 25 and 30', extending outside the outermost tube cylinder 9, are also situated in the plane of each group of tubes forming the skeleton.

The resulting heat exchanger is surrounded by a circular cylindrical casing 40 consisting of helically coiled tubes 41, 42 which are welded together to be gas-tight and which are connected to the headers 39, 38, respectively. The top of the casing 40 is bounded by a conical sheet-metal cap 46 in the center of which, a swirl-type muffle burner 45 is provided which is co-axial with the tube cylinders 4 to 9. The bottom end of the casing is closed by a sheet-metal hopper 47, which at the bottom end thereof merges into a flue gas duct 43 leading to a chimney (not shown). The sheet-metal cap 46 and hopper 47 are welded to the casing 40 so as to be gas-tight and the tubes of the heat exchanger and of the distributors 31-34 extend through the cap 46 and hopper 47 in gas-tight relationship. Those ends of the tubes forming the tube cylinders which are adjacent the burner 45 radiate outwards and surround the burner muffle as shown in the case of the tubes l, 2, 3 of the inner tube cylinder 4 and the skeleton tubes 11 and 16 (cf, FIG. l).

Gaseous or liquid fuel is burnt in the muffle burner 45 with a minimum of excess air so that combustion is complete inside the muffle and only hot gas, i.e., no flames, emerges from the muffle. ln addition, a space is formed between the muffle outlet and the tube cylinders 4 to 9 in which the gas leaving the muffle can be distributed uniformly over the heated tubes of the heat exchanger to heat the tubes by convection. The axial length of this gas distribution space is less than 1.5 times the inside diameter d of the muffle of the burner In order to prevent the flue gas from flowing mainly through the innermost tube cylinder 4, a throttle means is provided at the bottom end of the tube cylinder. This throttle means is in the form of a cylindrical sheetmetal cap 44 having a slightly smaller diameter than the inside diameter of the tube cylinder 44 and having apertures 48 for passage of the gas in the cylindrical wall thereof.

Instead of being disposed vertically as shown, the heat exchanger may be disposed horizontally. The tubes forming the skeleton may also be coiled helieally instead of being rectilinear, the direction of coiling of these tubes being in opposition to that of the tubes of the tube cylinders 4 to 9. Also, instead of all the heat exchange tubes being connected in parallel as illustrated, the tube system forming the skeleton and the tube system forming the tube cylinders may be connected in series in the flow of the heat-absorbing medium, with the system forming the skeleton being situated upstream of the system forming the tube cylinders.

What is claimed is:

l. A heat exchanger comprising means for producing a heated gas;

a first tube system for conducting a heat exchange medium to be heated by convection spaced from said means, said system including a plurality of coaxial tube cylinders, each cylinder consisting of at least one helieally coiled tube and the innermost tube cylinder of said system having contiguous coils therein and being coaxial with said means for producing a heated gas;

a second tube system for conducting the heat exchange medium spaced from said means to be heated by convection, said second tube system including a skeleton of tubes interposed between adjacent ones of said cylinders of said first tube system to space said cylinders from each other;

a distributor at one end of said tube cylinders connected to said skeleton of tubes; and

means within said innermost tube cylinder of said first tube system and at one end thereof for throttling a flow of the heated gas therethrough.

2. A heat exchanger as set forth in claim l wherein said tubes of said skeleton of tubes are substantially parallel to a longitudinal axis of said tube cylinders.

3. A heat exchanger as set forth in claim l wherein said tubes of said skeleton of tubes are arranged in groups in radial planes.

4. A heat exchanger as set forth in claim 3 which further comprises a plurality of distributors and a plurality of headers, each said distributor being connected to a respective one of said groups of tubes of said skeleton of tubes at one end thereof and each said header being connected to a respective one of said groups at an opposite end thereof.

5. A heat exchanger as set forth in claim 4 wherein said throttle means comprises a cylindrical cap having a slightly smaller diameter than the inside diameter of said innermost tube cylinder and having apertures therein for passage of the heated gas therethrough.

6. A heat exchanger as set forth in claim 1 which further includes a cylindrical casing of tubes welded together in sealing-tight relationship and surrounding said tube cylindersof said first tube system.

7. A heat exchanger as set forth in claim 6 wherein said tubes of said casing are helieally coiled.

8. A heat exchanger as set forth in claim l wherein said tube cylinders are connected in parallel for the flow of the heat exchange medium.

9. A heat exchanger as set forth in claim 1 wherein said tube cylinders and said tubes forming said skeleton of tubes are connected in parallel for the flow of the heat-exchange medium.

10. A heat exchanger as set forth in claim 1 wherein said means is a muffle burner having an axis parallel to a longitudinal axis of said tube cylinders.

1 l. A heat exchanger as set forth in claim l0 wherein said tubes of said tube cylinders radiate outwardly at the ends of said cylinders adjacent said burner to surround said burner, said tubes being connected with said tubes of said skeleton of tubes to a common distributor.

12. A heat exchanger as set forth in claim ll which further comprises a distribution space for the heated gas between an outlet of said muffle burner and said tube cylinders.

13. A heat exchanger as set forth in claim 12 wherein the axial length of said disribution space is less than 1.5 times the inside diameter of the muffle of said mule burner.

I* Ik UNITED STATES PATENT OFFICE D CERTIFICATE OF CORRECTION Patent: No. 3,757,7146' Dated` September 1l. 1973 HARENDA NATH SHARAN Inventor(s) It is certified that error appears in the above-identified `patent and that said Letters `Patent are hereby corrected as shown below:`

Column lines 6l to 62, delete "thereby. .convection". t Column l', line `6M, insert after "from the muffle, t" y --therefny allowing the tube systems to be heated Signed l,and sealed this Sth `@hay of' March 1971;.;

1 (SEALY Attest: e

EDWARD MTLECPGHERJR- C MARSHALL DANN Attesting Ofrflce Commissioner of Patents FORM podosouo'm I l uscoMM-Dc l01am-mw t U.S. GOVERNMENT PRINTING OFI'ICE Il. O-lll-l 

1. A heat exchanger comprising means for producing a heated gas; a first tube system for conducting a heat exchange medium to be heated by convection spaced from said means, said system including a plurality of co-axial tube cylinders, each cylinder consisting of at least one helically coiled tube and the innermost tube cylinder of said system having contiguous coils therein and being coaxial with said means for producing a heated gas; a second tube system for conducting the heat exchange medium spaced from said means to be heated by convection, said second tube system including a skeleton of tubes interposed between adjacent ones of said cylinders of said first tube system to space said cylinders from each other; a distributor at one end of said tube cylinders connected to said skeleton of tubes; and means within said innermost tube cylinder of said first tube system and at one end thereof for throttling a flow of the heated gas therethrough.
 2. A heat exchanger as set forth in claim 1 wherein said tubes of said skeleton of tubes are substantially parallel to a longitudinal axis of said tube cylinders.
 3. A heat exchanger as set forth in claim 1 wherein said tubes of said skeleton of tubes are arranged in groups in radial planes.
 4. A heat exchanger as set forth in claim 3 which further comprises a plurality of distributors and a plurality of headers, each said distributor being connected to a respective one of said groups of tubes of said skeleton of tubes at one end thereof and each said header being connected to a respective one of said groups at an opposite end thereof.
 5. A heat exchanger as set forth in claim 4 wherein said throttle Means comprises a cylindrical cap having a slightly smaller diameter than the inside diameter of said innermost tube cylinder and having apertures therein for passage of the heated gas therethrough.
 6. A heat exchanger as set forth in claim 1 which further includes a cylindrical casing of tubes welded together in sealing-tight relationship and surrounding said tube cylinders of said first tube system.
 7. A heat exchanger as set forth in claim 6 wherein said tubes of said casing are helically coiled.
 8. A heat exchanger as set forth in claim 1 wherein said tube cylinders are connected in parallel for the flow of the heat exchange medium.
 9. A heat exchanger as set forth in claim 1 wherein said tube cylinders and said tubes forming said skeleton of tubes are connected in parallel for the flow of the heat-exchange medium.
 10. A heat exchanger as set forth in claim 1 wherein said means is a muffle burner having an axis parallel to a longitudinal axis of said tube cylinders.
 11. A heat exchanger as set forth in claim 10 wherein said tubes of said tube cylinders radiate outwardly at the ends of said cylinders adjacent said burner to surround said burner, said tubes being connected with said tubes of said skeleton of tubes to a common distributor.
 12. A heat exchanger as set forth in claim 11 which further comprises a distribution space for the heated gas between an outlet of said muffle burner and said tube cylinders.
 13. A heat exchanger as set forth in claim 12 wherein the axial length of said disribution space is less than 1.5 times the inside diameter of the muffle of said muffle burner. 